Author Topic: BIAB infusion mash volume & temp numbers are way off  (Read 9005 times)

Offline weirdboy

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BIAB infusion mash volume & temp numbers are way off
« on: February 20, 2012, 02:57:15 PM »
This past weekend I attempted my first BIAB batch in about three years.
5 gallon batch size, with 10 pounds of grain, and a target mash temp of 154F with a 90 minute boil.

Beersmith reported the target volume as 9.1 gallons...I assumed initially that this was somehow meaning the combined volume of the water and grain, but when reading the mash specifics, it says to add 36.45 quarts of strike water at 163F. It then goes on to say the estimated post-boil volume is 6.25 gallons. Maybe that is also including the volume of the grain (which doesn't make sense)?


Just looking at the numbers, I knew something was wrong with the calculations, so I added 8 gallons of water instead of the recommended 9, and still ended up having to boil an extra 30 minutes or so to get to my target volume/gravity. Intuitively I also thought the strike water temperature sounded high, but I figured with the lower volume, maybe it would be OK...I was wrong. I ended up at a mash temp of over 160F after doughing in, and had to make quick adjustements while recirculating in order to get the mash temp down to the expected range.


Also, in general I feel like the "brewsheet" and "recipe" instruction boilerplate for mashing/boiling works OK for a typical 2 or 3 vessel system, but for BIAB the numbers, descriptions of the process, etc. don't work and I found them to be confusing. Thankfully, I have done it before, so it wasn't an issue as I just ignored them for the most part, but for new AG brewers, this would be a serious problem.

Offline enkamania

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Re: BIAB infusion mash volume & temp numbers are way off
« Reply #1 on: February 22, 2012, 09:24:57 PM »
I agree with you.  I some "jimmyed" it to get close to what I want, but it adds a sparge step to my brewsheet.

Offline lcf8088

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Re: BIAB infusion mash volume & temp numbers are way off
« Reply #2 on: March 07, 2012, 07:44:53 AM »
I wonder if they are aware of this problem and working to correct it.

Offline tom_hampton

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Re: BIAB infusion mash volume & temp numbers are way off
« Reply #3 on: March 07, 2012, 09:11:02 AM »
I don't BIAB, so take this with a grain of salt....I see three different issues:

Strike Volume: BS2 has a grain absorbtion parameter on the Options|Advanced tab that is specifically for BIAB vs. traditional mashtun-lautering.  It reflects the amount that you squeeze the bag, post mash.   If you take good notes and measure strike/pre-boil volumes, you should be able to do the math pretty easily.

Mash-Temp:  For BS2 to do the thermal calculations properly, it needs to know the actual temperature of your grain and your equipment (BIAB kettle).  In addition, it needs to know the mass (weight) and specific heat of your kettle.  There are recommendations on the equipment profile page based on the material.  Given that your mash-temp was high even though you used less strike-water I'd say that probably all of the above are contributors.  Perhaps BS2 thinks that your kettle is at room temp, not strike temp? 

Post-boil volume: BS2 calculates your post-boil volume from your equipment profile based on trub/dead space losses, and shrinkage (~4% from boil to fermentation temp).  It does not include the grain volume.  So, if BS2 is telling you that your post-boil volume is 6.25 gallons...it thinks that your will lose 4% to shrinkage (1 qt), and 1 gallon due to losses transferring from kettle to fermenter.  1 gallon trub/transfer loss is on the high side, but if you are using a keggle with a rounded bottom or a side-pickup it is conceivable. 

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Re: BIAB infusion mash volume & temp numbers are way off
« Reply #4 on: March 07, 2012, 09:37:59 AM »
Hi,
  I've had some reports like this but in every case I've been able to track to date the problem was actually in the equipment settings.  If you would like to send me a sample recipe with the problem I can take a look at it and try to identify the problem.  Please send it via email to beersmith at my beersmith.com domain.

Thanks,
Brad
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Offline jamie3

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Re: BIAB infusion mash volume & temp numbers are way off
« Reply #5 on: March 21, 2012, 01:02:21 PM »
This problem was really messing me up.

A work around for now is to do the following:

1) Manually enter the pre-boil volume. For a 5.5 gallon batch I set it to 7 gallons for 60 min boil. My setup is approx 1.5 gallons rate / hour evaporation rate.
3) Look at the mash setup. Beer smith will automatically add the additional water (e.g. grain absorption...) required for the BIAB mash method.


Offline rdewsbury

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Re: BIAB infusion mash volume & temp numbers are way off
« Reply #6 on: March 21, 2012, 02:58:57 PM »
If you follow the BIABinfo site guidelines for grain absorption, you will see quoted figures such as 1.3-1.4 L/kg which is around 1.25-1.33 pints/lb of grain.  The range takes into account how much you squeeze the heck out of your bag at the end and to an extent the coarseness of your grain mill setting.

In other words, they have determined that when you mash in the bag, the grain absorbs more than it's own weight in water.  Using this method can get efficiencies in the high 90s according to their reports, as long as you stick with a single vessel and don't lose stuff transferring between a mash tun and the kettle - hence the use of the bag I  the kettle to save gear.

Unfortunately, I cannot pull up my BIAB log records to confirm that , as the beer smith 1 disk died, but it does sound about right.  Hence your 36 odd quarts is 9 galling for 10 lb of grain.  Not too far off , albeit a little low, probably as it relies on rinsing the grains with additional Sparge water.

A simple way to start testing this is to measure your volumes pre mash in and after the bag is squeezed.  At that point, you can add water to the start level of 6.75 gallons with impunity, and then use the normal setup you have already determined for boil off etc for the rest of the session.


Offline rdewsbury

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Re: BIAB infusion mash volume & temp numbers are way off
« Reply #7 on: March 21, 2012, 07:34:54 PM »
 Belay that comment, I got my figures messed up.  Sorry about that.

Given the conversion numbers that I did hours before posting on the back of an envelope, I should have seen that 10 lb of grain would use 12.5-13 pints, not gallons as the absorption figure. 

So if you started at your system start volume of 6-7 gallons then add another 1 1/2 gallons before dough-in, you should be about there.    I have an 8 gallon kettle and it was sorely tested when I did a big 16lb grain) beer as BIAB with all the water.

Offline weirdboy

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Re: BIAB infusion mash volume & temp numbers are way off
« Reply #8 on: May 25, 2012, 11:38:05 AM »
Hi,
  I've had some reports like this but in every case I've been able to track to date the problem was actually in the equipment settings.  If you would like to send me a sample recipe with the problem I can take a look at it and try to identify the problem.  Please send it via email to beersmith at my beersmith.com domain.

Thanks,
Brad


Brad,

I have sent you an email with my brew log from that batch. I have since written my own BIAB calculator in excel which I have been using since then. My calculator hits the numbers every time; at least on my system, and others who have used it that I shared it with.  I have still been using Beersmith to formulate recipes and keep a brew log, but on brew day I have been using my calculator and completely ignoring the Beersmith brewsheet, which I used to print out and follow religiously.